1. Field of the Invention
This invention relates to new process and reactor designs including permeable reactors (permreactors) and permeators for the hydrocarbon steam reforming, hydrocarbon carbon dioxide reforming, combined hydrocarbon steam and carbon dioxide reforming, alcohol steam reforming, water gas shift, paraffin dehydrogenation, methanol synthesis, and combination of these conversion reactions for production of valuable fuels and chemicals. It also relates to the utilization of the end reaction products such as pure hydrogen, hydrogen and carbon monoxide, hydrogen and carbon dioxide, and mixtures of these species, into specific applications such as fuel cells, gas turbines, gas engines and synthesis reactors.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
This current invention describes new and improved process and reactor designs which involve permeable reactors (permreactors) and permeators for the hydrocarbon steam reforming, hydrocarbon carbon dioxide reforming, combined hydrocarbon steam and carbon dioxide reforming, alcohol steam reforming, the water gas shift reaction, dehydrogenation reactions of hydrocarbons, such as dehydrogenation of alkanes (i.e., paraffins) to alkenes, and combination of these previous reactions.
The reactions and heats of reactions that are referred to and utilized within the embodiments of the invention are well known and are listed below:    (1) CH4+H2O═CO+3H2 (ΔH0298=206.1 kJ/mol), methane-steam reforming    (2) CH4+CO2═2CO+1H2 (ΔH0298=247.3 kJ/mol), methane-CO2 reforming    (3) CO+H2O═CO2+H2 (ΔH0298=41.15 kJ/mol), water gas shift    (4) CnH2n+2═CnH2n+H2 (endothermic dehydrogenation reactions, heat of reaction varies depending on the type of feedstock processed in the reactor, e.g., ethane, propane, butane, pentane)    (5) CO+2H2═CH3OH (ΔH0298=−128.2 kJ/mol), methanol synthesis    (6) CO2+3H2═CH3OH+H2O (ΔH0298=−49.5 kJ/mol), methanol synthesis    (7) CH3OH+H2O═CO2+3H2 (ΔH0298=49.5 kJ/mol), methanol-steam reforming
These are catalytic reactions utilizing catalysts such as nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), chromium (Cr), copper (Cu), zinc (Zn), Cobalt (Co), Gold (Au) and other metals, and bimetallic catalyst compositions of these metals. The catalysts are supported on alumina (Al2O3), titania (TiO2), silica (SiO2), zirconia (ZrO2), lanthanum (La2O3) and other supports, enriched with earth metals such as Ca, La, Na, K.
Use of reactor and membrane permeator configurations and systems disclosed in our previous U.S. patent application Ser. No. 08/595,040, increase the overall process efficacy by increasing the total conversion of the following feedstocks: hydrocarbon, hydrocarbon-CO2 mixtures, methane, methane-CO2 mixtures, alcohols. Moreover, the yields to hydrogen and carbon monoxide or hydrogen and carbon dioxide are increased by the use of the integrated membrane permeators which separate effectively H2 and CO2 gases. Process efficiency is further improved by the recycling of unreacted and non-separated (non-permeated) hydrocarbon (e.g., methane) and carbon monoxide into the first (primary) reactor (reformer) or the alternative direction of the same stream into a consecutive catalytic reactor (reformer or water gas shift reactor) for additional production of hydrogen and carbon dioxide. Direct utilization of the produced and separated hydrogen, synthesis gas, and hydrogen-carbon dioxide mixtures from these processes into consecutive synthesis reactors, fuel cells and gas turbines and engines are additional advantages and continual applications of the proposed processes.
Current invention elaborates on the substitution of the primary conventional reactor (i.e., reformer, water gas shift, dehydrogenation reactor) by a permeable (membrane-type) reactor (so called permeator for simplicity) of specific design, and the correspondingly derived improved process and permeable reactor-separator configurations for the above mentioned reactions. Moreover, introduction and specification of double wall permreactors, besides the single wall permreactors, for conducting similar reactions are also disclosed. The described permreactors are designed to consist of interconnected parts which can be readily taken apart and assembled when service is necessary. For the disclosed integrated reaction-separation systems specific applications are disclosed such as the utilization of the end products and/or permeated (separated) streams into consecutively place synthesis reactors (including additional reformers or water gas shift reactors), gas turbines and engines, and various types of hydrogen based fuel cells and related fuel cell systems.
Previous reactor and permeable reactor designs from the above cited references refer mainly to methane and methanol steam reforming reactions but not to carbon dioxide reforming, water gas shift and dehydrogenation reactions as the present invention does. Moreover, previous inventions refer to a single reactor or permreactor or other reaction vessel instead of reactor-separator systems as the present invention describes. Present invention introduces double permeable-wall (double membrane-wall) reactors for hydrocarbon and alcohol processing reactions. The double membrane-wall reactors can be of various designs as disclosed within the embodiments of the invention. These can be catalytic reactors as adapted to specific process requirements in terms of setting key operating variables such as reaction temperature, pressure, space velocity, feed composition, to deliver final products (i.e., hydrogen and synthesis gas) in the purity and throughput required by consecutive applications. Moreover, flexibility in the selection of permreactor wall materials such as metals, inorganics, organics and composites, allows design of multifunctional permeable reactors which separate and deliver specific species (e.g., gases) with the required purity and throughput to consecutive applications. Flexibility in the selection of functional and specific permreactor wall materials for each process operation has also economic advantages. Current disclosed permreactor, separator, and overall process designs can utilize membrane materials selected from classes of metals, inorganics (non-porous or porous), polymers, carbons and carbonaceous materials, and composites. Therefore, the selection of less expensive membrane materials for a specific permreactor, permeator and process operation is available with current invented designs.
Present invention also teaches direct utilization of end product streams to consecutive synthesis reactors, fuel cells, gas turbines and gas engines. Present invention focuses on converting and upgrading primary hydrocarbon feedstocks such as methane, natural gas, coal gas, refinery feedstocks such as naphtha and alcohol feedstocks such as methanol and ethanol to higher calorific value hydrogen and carbon oxide mixtures; also it focuses on converting secondary and waste hydrocarbon feedstocks such as acidic natural gas, biomass gas to same valuable end products. Therefore, present invention describes environmentally benign reactor designs and process designs which abate and upgrade at the same time otherwise waste gases to valuable hydrogen, synthesis gas, hydrogen and carbon dioxide mixture. In situ conversion of carbon dioxide containing hydrocarbon mixtures and abatement of the carbon dioxide negative atmospheric and terrestrial greenhouse effect can be considered an additional benefit from the implementation of the invention.